Standard requirements for coating thickness of PCB conformal paint
The normal coating thickness of most circuit board products is 25 to 127 microns, and the coating thickness of some products is lower.
How to measure with the tool
Circuit boards must be protected with the thinnest possible coating material to minimize heat trapping, additional weight gain, and various other issues. There are three main methods to measure the thickness of conformal coatings.
Wet Film Thickness Gauge – Wet film thickness can be measured directly with a suitable gauge. These gauges consist of a series of notches, with each tooth having a known calibrated length. Place the gauge directly on the wet film to take a thin film measurement, then multiply that measurement by the percent solids of the coating to calculate the approximate dry coating thickness.
Micrometers – Micrometer thickness measurements are taken at several locations on the board before and after coating occurs. The cured coating thickness was subtracted from the uncoated thickness and divided by 2 to give the thickness of one side of the board. The standard deviation of the measurements is then calculated to determine the uniformity of the coating. Micrometer measurements are best with harder coatings that do not deform under pressure.
Ultrasonic Thickness Gauge – This gauge uses ultrasonic waves to measure coating thickness. It has an advantage over eddy current probes because it does not require a metal backplate. The thickness depends on the amount of time it takes for sound to travel from the transducer, through the coating, and reflect off the surface of the PCB. This method is relatively safe and will not damage the PCB.
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Post time: May-05-2023